Shock assisted ionization injection in laser-plasma accelerators

Thaury, C.; Guillaume, E.; Lifschitz, Agustín; Phuoc, K. Ta; Hansson, Martin; Grittani, G.; Gautier, J.; Goddet, J. P.; Tafzi, Amar; Lundh, Olle; Malka, Victor

doi:10.1038/srep16310

Cited by 76 publications

(59 citation statements)

References 28 publications

(36 reference statements)

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“…For electron densities much lower than the so-called critical density (i.e.,  w º  n n m e e c e 0 0 2 2 , where w 0 is the laser frequency, e the electron charge, m e the electron mass and  0 the permittivity of vacuum), the laser pulse can propagate large distances ( l p w º  L c 2 0 0 ) through the plasma and generate a strong wakefield [15][16][17][18][19][20][21][22][23]. This high-velocity (ṽ c) plasma wave can trap part of the background electrons and, for optimized laser-plasma parameters, accelerate them to ultrarelativistic energies with possibly narrow energy spectra [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. The resulting electron beam, with charge in the nC range, can also act as an efficient x-ray generator [41].…”

Section: Introductionmentioning

confidence: 99%

Electron heating by intense short-pulse lasers propagating through near-critical plasmas

et al. 2017

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We investigate the electron heating induced by a relativistic-intensity laser pulse propagating through a near-critical plasma. Using particle-in-cell simulations, we show that a specific interaction regime sets in when, due to the energy depletion caused by the plasma wakefield, the laser front profile has steepened to the point of having a length scale close to the laser wavelength. Wave breaking and phase mixing have then occurred, giving rise to a relativistically hot electron population following the laser pulse. This hot electron flow is dense enough to neutralize the cold bulk electrons during their backward acceleration by the wakefield. This neutralization mechanism delays, but does not prevent the breaking of the wakefield: the resulting phase mixing converts the large kinetic energy of the backward-flowing electrons into thermal energy greatly exceeding the conventional ponderomotive scaling at laser intensities > -10 W cm 21 2 and gas densities around 10% of the critical density. We develop a semi-numerical model, based on the Akhiezer-Polovin equations, which correctly reproduces the particle-in-cell-predicted electron thermal energies over a broad parameter range. Given this good agreement, we propose a criterion for full laser absorption that includes field-induced ionization. Finally, we show that our predictions still hold in a two-dimensional geometry using a realistic gas profile.

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Section: Introductionmentioning

confidence: 99%

Electron heating by intense short-pulse lasers propagating through near-critical plasmas

et al. 2017

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“…However, this type of trapping typically occurs over an extended length, and the electron energy distribution is therefore usually wide. Methods to localize ionization-induced injection and thereby generate quasi-monoenergetic electron energy spectra are certainly of interest including self-truncation of ionization-induced trapping and ionization-induced trapping in a shock [16,17].…”

Section: Introductionmentioning

confidence: 99%

Localization of ionization-induced trapping in a laser wakefield accelerator using a density down-ramp

Hansson

Audet

Ekerfelt

et al. 2016

Plasma Phys. Control. Fusion

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We report on a study on controlled trapping of electrons, by field ionization of nitrogen ions, in laser wakefield accelerators in variable length gas cells. In addition to ionization-induced trapping in the density plateau inside the cells, which results in wide, but stable, electron energy spectra, a regime of ionization-induced trapping localized in the density down-ramp at the exit of the gas cells, is found. The resulting electron energy spectra are peaked, with 10% shot-to-shot fluctuations in peak energy. Ionization-induced trapping of electrons in the density down-ramp is a way to trap and accelerate a large number of electrons, thus improving the efficiency of the laser-driven wakefield acceleration.

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“…Several techniques to improve the beam quality have been adopted e.g. the use of dual-stage targets of injector and accelerator [53,54], a combination of ionization and shock-front injection [55], ionization induced injection in a density down ramp [56] where quasi-monoenergetic electron beams have been observed.…”

Section: Introductionmentioning

confidence: 99%

Direct laser acceleration of electrons in a high-Z gas target and the effect of threshold plasma density on electron beam generation

Hazra

Moorti

Mishra

et al. 2019

Plasma Phys. Control. Fusion

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An experimental study of laser driven electron acceleration in N 2 and N 2 -He mixed gas-jet target using laser pulses of duration ~60-70 fs is presented. Generation of relativistic electron beam with quasi-thermal spectra was observed at a threshold density of ~1.6×10 18 cm -3 in case of pure N 2 , and the threshold density was found to increase with increasing doping concentration of He.At an optimum fraction of 50% of He in N 2, generation of quasi-monoenergetic electron beams was observed at a comparatively higher threshold density of ~2×10 18 cm -3 , with an average peak energy of ~168 MeV, average energy spread of ~21%, and average total beam charge of ~220 pC. Electron acceleration could be attributed to the direct laser acceleration as well as the hybrid mechanism. Observation of an optimum fraction of He in N 2 (in turn threshold plasma density) for comparatively better quality electron beam generation could be understood in terms of the plasma density dependent variation in the dephasing rate of electrons with respect to transverse oscillating laser field. Results are also supported by the 2D PIC simulations performed using code EPOCH.

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Shock assisted ionization injection in laser-plasma accelerators

Cited by 76 publications

References 28 publications

Electron heating by intense short-pulse lasers propagating through near-critical plasmas

Electron heating by intense short-pulse lasers propagating through near-critical plasmas

Localization of ionization-induced trapping in a laser wakefield accelerator using a density down-ramp

Direct laser acceleration of electrons in a high-Z gas target and the effect of threshold plasma density on electron beam generation

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